Difficulties in Seismic Hazard in Colombia Due to the Scarcity of Instrumental Data

Abstract

This paper presents a probabilistic assessment of seismic hazard in Colombia, using data covering the period from 1960 to 2010 in the area between longitudes 80° W to 70° W and latitudes -1° N to 15° N. Recurrence laws and seismic hazard curves in areas of 2° by 2° were evaluated. In making the recurrence curves, quadrants in which there are insufficient data to have a slightly acceptable result were found. The seismic hazard curves were subsequently developed by using the Fukushima and Tanaka attenuation equations 1990). Finally an iso-acceleration curve map was developed for Colombia, which shows that there are areas for which no value can be assigned from the probabilistic point of view. Evaluations were performed using algorithms developed by the author. Peak accelerations on rock, estimated for a return period of 475 years, range from 438 gals in the Pacific coast, in the swarn of Uraba, and at the border with Ecuador, to 270 gals in the Middle Magdalena. There is no consensus for assigning threat levels in areas prone to seismic activity with catastrophic historical events but limited historical and instrumental data. Recent events in Haiti (2010) is one example of areas where there is important historical background, although the instrumental seismological information is insufficient